The Arizona Cardinals are now on the search for a new head coach and new franchise quarterback.

Carson Palmer, who missed the final nine games of his 15th NFL season due to a broken arm, has announced that he’s retiring in an open letter to Cardinals fans. Arizona posted it on the team’s Twitter page.

“Over the years, I’ve had teammates who decided to hang it up and I would ask them how they knew when it was time to walk away. The answer was almost always the same: You just know,” Palmer began.

“For me that time is now. Why? Quite simply, I just know.

“For 15 years I have been lucky enough to play quarterback in the NFL and it has been the most incredible experience of my life. There wasn’t one second that I took it for granted or failed to appreciate what a tremendous privilege it is.”

Palmer has played for the Cardinals for the last five years, starting 60 games. In 2015, he started all 16 games and Arizona was 13-3, advancing to the NFC Championship game, where it lost to the Panthers.

He had a stellar season, with career highs in yards, touchdowns and quarterback rating, and was named a Pro Bowler for the third and final time.

The Cardinals entered this season as a playoff contender, thanks to the return of Palmer, Larry Fitzgerald and running back David Johnson, who was a revelation in 2016. But Johnson and Palmer’s injuries as well as other key injuries on offense were crushing.

The No. 1 overall pick in 2003 out of USC, Palmer spent the first seven seasons of his career with the Cincinnati Bengals, where he went to the playoffs twice and the Pro Bowl twice. Despite being the Heisman Trophy winner in 2002 and the top pick, the Bengals opted to sit Palmer for his entire rookie year, as he learned from the coaches and veteran quarterback Jon Kitna.

His relationship with the Bengals ended poorly, with Palmer requesting to be traded after the 2010 season. Cincinnati president Mike Brown refused, and Palmer didn’t show up to training camp in 2011. But in October, the Oakland Raiders, desperate for a starting quarterback after an injury to Jason Campbell, offered first- and second-round picks, and the Bengals agreed to the deal.

Palmer spent two seasons with the Raiders before being traded to Arizona in 2013.